[CVE-2026-90253][LOW] Bluetooth: MGMT: free the mesh send cancel command when it is cancelled [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-90253
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Bluetooth: MGMT: free the mesh send cancel command when it is cancelled [ Upstream
Commit: b609341ee56967d9a45845ff26f79336d2114b55
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b609341ee56967d9a45845ff26f79336d2114b55
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90253
Analysis date: Thu, 17 Sep 2026 14:20:39 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Bluetooth MGMT mesh send cancel can leak a pending command and pin the management socket reference when the queued command is cancelled during controller unregister, leading to possible local resource exhaustion rather than memory corruption or privilege escalation.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-90253 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90253

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-90253	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90253 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'Bluetooth MGMT mesh send cancel can leak a pending command object because mesh_send_cancel queued the command without a destroy callback. If the queued entry is later cancelled during HCI controller unregister, hci_cmd_sync_clear does not release entry data and the mgmt_pending object also keeps the socket reference pinned. For the CVSS the PR:L is used in the paranoid score because an untrusted local actor would still need access to a Bluetooth management path or delegated network administration capability, while normal systems usually restrict this to privileged services. The issue is not network reachable and requires local control plane interaction with Bluetooth management and controller lifecycle events. Impact is resource exhaustion or socket reference leakage over repeated trigger cycles, not direct memory corruption or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	REMOTE INIT LEAK UAF NETWORK  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

## 1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

## 2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. The pending `mgmt_pending` command is not released when the queued entry is cancelled without a destroy callback, and the socket reference taken by `mgmt_pending_new()` remains pinned.
* +0 Reliable kernel crash / strong DoS not awarded. The supplied evidence shows a leak and unreleased socket reference, not an immediate panic, UAF, double free, or fatal fault.
* +0 Local unprivileged trigger not awarded. The complete trigger path through Bluetooth MGMT mesh cancellation and controller unregister is not proven reachable by an ordinary unprivileged user.
* +0 Remote reachability not awarded. This is a local Bluetooth management control-plane issue, not packet-triggered remote Bluetooth traffic processing.

Paranoid additional signal:

* +1 Potential accumulated availability impact. Repeated successful trigger cycles could accumulate leaked commands and pinned socket references, causing resource exhaustion over time.

Important non-awarded signals:

* RealUAF not awarded. The bug leaks an object/reference but does not establish post-free use of a stale object.
* Concrete repeated release/refcount not awarded. There is no first release followed by a second lifetime mutation on the same dangling reference.
* Controlled reclaim not demonstrated.
* Arbitrary read/write not demonstrated.
* Confidentiality and integrity impact not awarded.
* Structured stale-object leverage not awarded because there is no stale post-lifetime object consumption.
* Extra availability not awarded for the conservative score because only a leak is demonstrated, not immediate host-wide failure.
* No privilege-escalation signal is established.

## 3. Reachability analysis

The likely trigger is a local actor able to issue the Bluetooth MGMT mesh send cancel operation and then cause or coincide with HCI controller unregister, which leads `hci_cmd_sync_clear()` to cancel pending entries.

The supplied patch does not include the relevant Bluetooth MGMT permission checks, so host-admin-equivalent privilege for the complete trigger is not positively established. It is also not proven that an ordinary unprivileged user can perform the complete operation. Therefore `HostAdminRequired=UNKNOWN`.

No namespace-scoped capability path is established. Bluetooth controller management is not shown here to be fully network-namespace scoped, so `NamespaceScopedPrivilege=NO`.

There is no direct network trigger. The issue requires local control-plane interaction with Bluetooth management state and controller lifecycle events. No special rare hardware penalty is applied because the patch does not establish a rare physical-only prerequisite, but practical exposure depends on Bluetooth Mesh support and controller management availability.

Race repeatability is not the central issue. The bug is mainly a cancellation/cleanup path leak caused by a missing destroy callback.

## 4. Primitive and severity interpretation

The exact primitive is a persistent kernel object/reference leak. `mesh_send_cancel()` queued a command with a NULL destroy callback. If the queued entry was cancelled, `_hci_cmd_sync_cancel_entry()` did not release `entry->data`, and the `mgmt_pending` object also kept the associated management socket reference alive.

This is not an active structured UAF and not fixed stale storage UAF. It is a resource lifetime cleanup failure. The demonstrated consequence is leaked memory and a pinned socket reference. The speculative consequence is gradual resource exhaustion after repeated trigger cycles.

Primitive class is `CLASS_C` because the behavior is primarily DoS/resource leak oriented without an independently useful corruption primitive.

ImportantCandidate is `NO` because there is no UAF, no repeated lifetime mutation through dangling storage, no controlled reclaim, no authorization bypass, and no demonstrated privilege escalation.

AutoDowngradeAllowed is `YES` because the issue is a local resource/reference leak with no unresolved memory-corruption or security-boundary primitive.

Likely operational severity is Low-like to ordinary Moderate.

## 5. One-sentence report phrase

Bluetooth MGMT mesh send cancel can leak a pending command and pin the management socket reference when the queued command is cancelled during controller unregister, leading to possible local resource exhaustion rather than memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a concrete local resource/reference leak without UAF, double release, arbitrary read/write, authorization bypass, remote reachability, or demonstrated privilege escalation.

## 7. Call-site confidence

Call-site confidence: high

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: Bluetooth: MGMT: free the mesh send cancel command when it is cancelled [ Upstream
Commit: b609341ee56967d9a45845ff26f79336d2114b55
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b609341ee56967d9a45845ff26f79336d2114b55

Changed files:
  net/bluetooth/mgmt.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b609341ee56967d9a45845ff26f79336d2114b55

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-90253 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90253

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 1
  Paranoid ActionableScore: 2

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).